Method and apparatus for mixing a furnace charge



C. HART Feb. 14, 1933.

METHOD AND APPARATUS FOR MIXING A FURNACE CHARGE Filed Dec. 6, 1950 2Sheets-Sheet l Feb. 14, 1933. c. HART METHOD AND APPARATUS FOR MIXING AFURNACE CHARGE Filed Dec. 2 Sheets-Sheet 2 Patented Feb. 14, 1933 UNITEDSTATES PATENT OFFICE GEAR-LES- HART, OF MEDIA, PENNSYLVANIA, ASSIGNOR,BY MESNE ASSIGNMENTS, TO WILLIZL'M STEEL JACKSON, 01 PHILADELPHIA,PENNSYLVANIA METHOD AND APPARATUS FOR MIXING A FURNACE CHARGEApplication filed December 6, 1930. Serial No. 500,555.

My invention relates to methods of mixing furnace charges and to theinternal construction of rotatory and oscillatory mixingfurnaces.

A purpose of my invention is to turbulently mix the charge in a rotatoryor oscillatory furnace more vigorously than has previously beenpossible.

A further purpose is to cause the charge in 19 a mixing furnace tofollow a path during each revolution substantially longer than the innercircumferenceof the furnace.

A further purpose is to spirally dispose oppositely directed mixingvanes in the lining of a mixing furnace.

A further purpose is to construct a labyrinth path for the chargebetween adjacent oppositely directed vanes by extending one vane fromone end of the furnace part of the way only to the other end of thefurnace, and running the next vane from the latter end part of the wayonly to the first, so that the charge will frequently change itsdirection of flow.

A further purpose is to make the radial inward extension of a mixingvane less than. the depth of the charge pool: when lying in the bottomof the furnace so that the charge will repeatedly fold and lap: overitself asathe 39 furnace rotates instead of merely flowing bodily overan irregular surface;

A further purpose is'to overflow the-charge carried up by each vane inthe form of a thin sheet, and to rumple up the sheet against the nextvane in the advancing quadrant of the furnace in contact with the chargeflowing longitudinally ofthe furnace against that vane, toinject thehigh velocity overflow stream into the low velocity longitudinal stream.

A further purpose is to arrange the stirring vanes in a mixing furnaceso. that portions of the charge will be directed by one vane against thenext succeeding vane at a point 43 near that atwhich the nextvaneprojects'from the end wall, and, after abruptly changingdi motion,will be carried along that vane-gem orally longitudinally of the furnacetoward the opposite end wallbefore they can progress radially to anysubstantial extent.

A further purpose is to cascade charge material from one vane to anotheron the advancing side of a furnace before the charge can join the poolin the bottom of the furnace, and to inject the cascading flow at highvelocity into the pool when it-reaches thesurface of the pool.

A. further purpose is to rotate the puddled ball in an axial directionto make it spherical rather than ellipsoidal.

Further purposes will appear in the specification and in the claims.

In the drawings I illustrate one of many possible forms embodying myinvention, choosing a form which is advantageous in practice andconvenient for illustration and for explanation of the principlesinvolved.

Figure 1 is a sectional elevation of a mixing furnace, the section beingtaken along the line 1-1 of Figure 2'.

Figure 2 is a section of Figure 1 on the line 2'--2, omitting structurein the background.

Figure 3 is a fragmentary section taken on the line 33 of Figure. 1.

Figure f is a fragmentary section taken upon the line 4-4 of Figure 1. s

Figure 5 corresponds'generallyto Figure 2, omitting. the externalstructure, and showing the furnace during the mixing of a; charge;

Figure 6 is a sectional perspective view ofthe' advancing side of thefurnace during the mixing of a charge. Other" structure is omitted.

Designers of mixing furnaces, especially of pud'dling' furnaces, havepreviously sug gcsted: the use of mixing vanes of many'chara'cters andforms. Generally these have extended longitudinally from: one end tothe: other of the furnace, and have been con-- structed so that thecharge will be momentarily dammed against the advancing edge of thevane, and will then flow in a thin sheet across the vane as the furnacecontinues to turn to permit the charge to rise above the vane.

While much superior to a. smooth: lining, mixing vanes of this type areinefficient v because" all parts of the charge to a large extent retain.the: samerelation to one another. 100

The same small portion will be repeatedly mixed, while other parts ofthe charge will not be kneaded and folded or lapped over themselves.

It has been suggested that the mixing vane should spiral continuouslyalong the furnace wall. In some ways the continuous spiral vane is muchmore advantageous than the form having the vane extending directlylongitudinally of the furnace.

A number of disadvantages are however apparent. The mixing vane shouldcompel the charge to take a path much longer than the furnacecircumference, but inthe continuous spiral form the path is only veryslightly longer because of the very fiat pitch of the spiral vane. Thespiral represents the diagonal merely of a triangle having thecircumference for one side, much longer than the pitch, which is theother side. The spiral should not be continuous, because the mixing ismuch more advantageous if the charge be compelled to change itsdirection frequently.

I find that intermingling and then intermixing charge taken from oneplace with charge from another place is very much better than merelyspirally progressing them. In this way, as the portions of charge arecarried over the vane or compelled to change direction, they will becomethoroughly mixed to produce a uniform composition. I preferably bringtogether portions of charge moving at different velocities.

By my invention I combine numerous desirable features lacking inprevious furnaces of this type in a construction which is easy to build,sturdy in use, and convenient to repair.

Among the advantageous features to be found in my form, I may mentionthe follow- .ing:-(1) during each rotation the charge traverses a longpath, several times the length of the circumference of the furnace; (2)the charge frequently changes direction abruptly; (3) parts of thecharge flow in sheets over the mixing vanes and are then rumpled upbefore being mixed farther; ('4) charge from one place is projected intocontact with that from another place; (5) the charge is kneaded, foldedand lapped overitself; (6) portions of the charge travelling at verydifferent velocities will be brought together, as when charge fallingfrom high up on the advancing side of the furnace meets chargetravelling longitudinally along one of the vanes, and penetrates by jetaction; (7) charge from the advancing side of the furnace cascades intocharge at the bottom of the furnace.

Referring to Figures 1 and 2, the furnace comprises generally anexternal metallic casing 15 supported at either end by the heads 16 and17 braced at 18 and 19 from the hubs 20 and 21. The hubs carry bands 22and 23 which rest in and rotate or oscillate upon rollers 24 and 25 insupports 26 through the burner 33 from the pipe 34, controlled by thevalve 35. Air is drawn in around the burner. The products of combustionfrom the furnace discharge through the neck 36 into the flue 37 and upthe stack 38. The flue and the neck are desirably sealed as at 39in anysuitable manner so that the furnace may rotate without excessive loss ofdraft.

For charging and discharging, the fur-' nace has a door 40, which mayvery desirably be mechanically controlled by the electric motor andspeed reduction units 41, as through the driving connections at 42. Themotors 41 impart rotation to the screws 43, supported in the bearings 44of'the collars 45. The collars 45 are'pivoted at 46 to the lifting arms47, pivotally secured to the furnace casing at 48. The lifting arms 47are secured to the door frame 40 at the pivotal and rotatable bearings49.

The refractory lining 50 covers the interior of the furnace body 15. Atthe inside of the door the refractory material 51 may very desirably besmooth in surface, since projections placed at this point would belikely to interfere with the opening of the door.

At 52 I illustrate a large projection into the furnace interior, andintend it to represent any of a number of projections which may be foundin mixing furnaces. I do not intend the shape of this projection to becritical. Thus 52 may be a breaking wall, a longitudinal mixing vane, askimming dam, or'

any other similar structure.

The use of an interior projection as a skimming dam is described andclaimed by me in my copending application Serial Number 461,100, filedJune 14, 1930. Skimmed material will collect in the pocket 53 near thedoor when the furnace is moved counter.- clockwise about 180 from theposition shown in Figure 2. The skimmings may then be dis charged simplyby opening the door.

The illustration of a skimming dam in the drawings is intended merely toshow that this may be desirably combined with stirring vanes in the samefurnace.

' The spiral mixing vanes 54 are desirably built up of refractorymaterial extending beyond the surface of the lining. The vanes run fromthe ends of the furnace at 55 to points 56 near the opposite ends of thefurnace.

The pitch I of the vane is preferably quite steep, and very desirablygreater than 45 so that a considerable component of the velocity ofcharge flowing along the vane will be longitudinal to project the chargeagainst the end ofthe furnace.

As will be seen best in Figure 4, the ends of the vanes at 56 taper downfrom points 57 to points 58, at which they blend with the adjacentrefractory lining. This enables the charge to flow more readily over thevane at the points 56 where it changes direction, and at the same timeprevents spalling and cracking of the refractory material at the end.

It will be evident that the pitch of the spiral of the vanes is verysteep. This I consider to be a distinct feature of utility in myinvention, as later explained.

When my furnace is operated, a number of very desirable types of mixingwill take place. Assuming that the direction of rotation in Figure 2 isclockwise, the vanes as seen in Figure 1 will be on the advancing sideof the furnace. The positions of any vane progressively rising on theadvancing side are 5s, 54 and 54 It will be understood that thesepositions are merely arbitrary ones along the circular path of eachvane, and that the fact that these positions were chosen to coincidewith the vanes in Figures 1 and 2 is merely a convenience inillustration.

From Figures 5 and 6 an approximate idea of the way mixing will takeplace may be formed. Of course the flow lines indicating the behavior ofthe charge are not intended to be more than illustrative, since theywill vary with the size and shape of the furnace and vanes, with thedensity, viscosity and quantity of the charge, and with the speed ofturning of the furnace.

Each vane as it sweeps past the lowest point of the furnace will pushbefore it a portion of the charge in the pocket 59. When the vanereaches the position 5d, and even before this time, charge material fromthe pocket will flow over the vane toward the bottom of the furnace,because the size of the pocket in front of the vane will progressivelydecrease as the vane advames. The sheet 61 of charge overflowing willfall bevond the vane into the pool 62 of charge at the bottom of thefurnace or into the portionof the charge being swept along by the nextvane.

The overflowing sheet of charge material will cause several kinds ofmixing. It will e place charge from the pocket 60 in contact with chargeat the bottom of the furnace. The sheet 61 of charge will fall atrelatively high velocity, while the pool 62 in the bottom of the furnacewill be substantially quieswnt,

'- so that the sheet will penetrate as a jet into the pool, mixing thesheet and pool.

hen the sheet 61 strikes the pool 62 it will rumple up, so that thevarious parts of the sheet will be mixed together. And, since thesurface of the vane is irregular, portions of the sheet will lap andfold over themselves before the sheet falls clear of the vane and intothe pool. All of these types of mixing will occur below the position 54due to falling of the charge into the pool.

Mixing will be still further increased as the vane under discussionmoves to the position 54 Here the space in the pocket 63 above the vane54 will be even smaller than was that in the pocket 60.. overflowingchargewill form in a sheet 64 and flow down. against the charge in thepocket 60 below.

The charge in the pocket 63 will undergo a number'of types of mixing.Due to the high velocity of its overflow sheet 64 with respect to thecharge in the pocket 60, it will penetrate that charge. by jet action tosome extent. The sheet 64; will rumple up and the charge in the pocket60 will be kneaded, folded and lapped over itself, just as was the sheet61 from the pocket 60 when it came into contact with the pool 62 at thebottom of. the furnace.

Part of the sheet ofcharge from'the pocket 63 will strike against thesurface of the lining or of the charge in the pocket 60 and be deflectedwithout substantial mixing in the pocket 60, merely changing itsdirection and passing over the vane 54" with the overflow sheet from thepocket 60. This portion 65 of the charge cascades from the upper pocketto the pool without undergoing intermediate mixing with other charge toany great extent. The process ofcascading, involving as it does lappingand. changing of direction, is very desirable from the standpoint ofthorough mixing of the cascaded material. It will be evident that thesheet of charge which penetrates the material in the pocket 60 willaugment that material, so that more charge will be supplied to theoverflow sheet from the pocket 60 than merely that expelled because ofthe decreased volume of that pocket on account of its angular change ofposition.

In the position 54 tosome extent, and to a greater extent in thepositions 54: and 54 charge will flow generally longitudinally of thefurnace from the points 55 to the points 56 on each vane. and 63,therefore, the charge will be moving longitudinally of the furnace.

Thus for example charge 66 in the pocket 61v will reach the point 56 onthe vane on the position 54 and, since it has considerable longitudinalvelocity, be projected against the end wall of the furnace. Here it willbe kneaded, folded and lapped over itself as it falls against the vanebelow in the position 54:. In the area 67 the charge will abruptlychange direction, with the consequent production of eddies and swirls.Charge will then continue along the pocket 60 toward the bottom of thefurnace, or join the overflow sheet 61.

Similarly the portion 68 of the charge will In each of the pockets 60'be carried from the vane in position 54 against the end wall, while anoverflow sheet 69 will fall from the Vane. Some of this sheet willrumple in the pocket 63, while other parts of it will cascade to thepool 62.

It will be evident that the path taken by the charge flowing generallylongitudinally will be much longer than the corresponding are traversedby the vane. The path is similar to a labyrinth in which the charge musttravel back and forth from one end to the other of the furnace before itcan move angularly the distance from one vane to the next. For moreeffective variation of the stirring produced, the vanes may differslightly in size and shape as shown.

The progress of the charge along the vanes will not be as simple as thisbecause the charge in any pocket will constantly be augmented by chargefrom the overflow sheet of the vane above and will constantly bedepleted by charge supplied to the overflow sheet from that pocket. Thecharge in the pocket will constantly be stirred by the jet action of theoverflow sheet falling against its surface, and will be agitated bycascading metal travelling from vane to vane.

It will be evident that all of the kinds of mixing discussed hereinserve to take charge material from one point and deposit it at anotherpoint, and then to incorporate together these different portions of thecharge. The difliculty of observing occurrences in the furnace makes itimpossible to further analyze the behavior of the charge during mixing.It will be understood that I do not restrict my invention to any theoryof operation, but merely include a discussion of the principles which Ibelieve to be involved in order to make more clear the disclosure of mybest form.

Figures 5 and 6 are to be considered only as illustrations from whichthe operation may be better understood.

lVhile I have described the mixing as taking place on the advancing sideof the furnace as if the furnace were being rotated continuously in onedirection. it will be understood that the same type of mixing will occurif the furnace be oscillated except that the advancing side will changefrom time to time.

Of course all of the types of stirring will take place simultaneouslyrather than successively, but for convenience I describe the occurrencesas displaced in time from one another.

When the puddled ball has been formed my mixing vanes serve anadditional purpose, for they cause the ball to roll. axially withrespect to the furnace, as well as circumferentially, making it assume aspherical rather than ellipsoidal shape.

Doubtless considerable advantage from my invention could be obtained byvarying the angles of the mixing vanes to suit special uses, or byplacing them diflerently with respect to the lining of the furnace. Inparticular this might be desirable with a charge whose viscosity variesconsiderably from that of wrought iron, for which the structure shown iswell suited.

In view of my invention and disclosure variations and modifications tomeet individual whim or particular need will doubtless become evident toothers skilled in the art, to obtain part or all of the benefits of myinvention without copying the structure shown, and I, therefore, claimall such in so far as they fall within the reasonable spirit and scopeof my invention.

Having thus described my invention, what I claim as new and desire tosecure by Letters Patent is:

1. The method of mixing a wrought iron puddling furnace charge in acylindrical furnace, which consists in flowing a portion of the chargein a narrow stream around the internal circumference of the furnace andalso endwise of the furnace in reversing the direction of endwise traveland in reuniting the narrow stream to the remainder of the charge.

The method of mixing a furnace charge which consists in flowing part ofthe charge along a zigzag path with frequent abrupt changes of directionwhile concurrently rumpling sheets of charge against the surface of thepart of the charge traversing the path.

3. The method of mixing a furnace charge which consists in flowing partof the charge along a zigzag path with frequent abrupt changes ofdirection while concurrently rumpling sheets of charge against the surface of the part of the charge traversing the path and progressing thecharge transverse to the path.

4. The method of mixing a furnace charge which consists in cascadingpart of the charge under the action of gravity with frequent changes ofdirection into contact with the surface of a relatively quiescent partof the charge.

5. The method of mixing a furnace charge which consists in flowing partof the charge generally horizontally and jetting another part of thecharge vertically into the part flowing horizontally to mix the twoparts together.

6. The method of mixing a furnace charge which consists in flowing partof the charge generally horizontally, jetting another part of the chargevertically into the part flowing horizontally and lapping the combinedflowing and jetted charge over itself to incorporate the two parts.

7. The method of mixinga furnace charge which consists in flowing partof the charge generally horizontally, jetting another part of the chargevertically into the part flowing horizontally and successively sheetingthe combined flowing and jetted charge and rumpling up the sheet toincorporate the two parts.

8. The method of mixing a furnace charge which consists in flowing partof the charge generally horizontally, jetting another part of the chargevertically into the part flowing horizontally and abruptly reversing thedirection of the combined flowing and jetted parts to incorporate them.

9. The method of shaping a puddled wrought iron ball against a surfacewhich consists in rolling it along a zigzag path over the surface.

10. The method of shaping a puddled wrought iron ball in the interior ofa lined cylindrical mixing furnace which consists in rolling it over thelining alternately in directions oppositely substantially diagonal tothe furnace axis.

11. The method of shaping a puddled ball in the interior of a linedcylindrical mixing furnace which consists in rolling it over the liningalternately in directions oppositely substantially diagonal to thefurnace axis, while arcuately progressing the ball in a directionopposite to one component of the velocity of rolling advance by rotatingsaid furnace.

12. In a rotatory or oscillatory mixing furnace, a furnace body, afurnace lining within the body, and a plurality of oppositely spiralledmixing vanes projecting from the lining.

13. In a rotatory or oscillatory mixing furnace, a furnace body, afurnace lining within the body, and a plurality of o positely spiralledmixing vanes projecting rom the lining and alternatively extending fromrespective ends of the lining part only of the distance to the oppositeends,

14. In a rotatory or oscillatory mixing furnace, a furnace body, afurnace lining within the body, and a plurality of mixing vanesprojecting from the lining and discontinuous at staggered points aboutthe lining, each vane extending the greater part of the distance fromone end of the furnace to the other.

15. In a rotatory or oscillatory mixing furnace, a furnace body, afurnace lining within the body, a plurality of oppositely spiralledmixing vanes about the lining and a projection from the lining extendinglongitudinally of the furnace.

16. In a rotatory or oscillatory mixing furnace, a furnace body, afurnace lining within the body and a plurality of oppositely spiralledmixing vanes about the lining having a pitch angle greater than 45.

17. The method of mixing a wrought iron puddling furnace charge in acylindrical furnace, which consists in flowing a portion of the chargein a narrow stream around the internal circumference of the furnace andalso of the charge.

CHARLES HART.

